A novel injectable scaffold for cartilage tissue engineering using adipose-derived adult stem cells

Articular cartilage has a limited self-regenerative capacity. Thus, treatment of cartilage lesions is a major challenge. Tissue engineering using a variety of biomaterials is a promising solution to the problem of cartilage damage. In this in vitro study, we investigated the effect of the presence of cartilage-tissue chondroitin-sulfate (CS) in a fibrin scaffold on the differentiation of adipose-derived adult stem cells (ADAS cells) into chondrocytes. Isolated rabbit ADAS cells were cultured in fibrin matrices with and without CS for up to 14 days. ADAS cells differentiated into chondrocytes in both matrices, but cell proliferation, glycoaminoglycans content, and type II collagen expression were significantly higher in the fibrin-CS matrices than those in the fibrin matrices alone. Histological examination and scanning electronic microscopy revealed the fibrin-CS matrices exceeded in inducing differentiation of ADAS cells into chondrocytes in terms of tissue morphological characteristics. We concluded that the fibrin-CS matrices mimicking native cartilage extracellular matrix could act as a three-dimensional scaffold for cartilage tissue engineering and have the potential for promoting ADAS cells differentiation into chondrocytes.

Differences in extracellular matrix production and basic fibroblast growth factor response in skin fibroblasts from sporadic and familial Alzheimer's disease

Extracellular matrix (ECM) molecules and growth factors, such as fibroblast growth factor (FGF), play a crucial role in Alzheimer's disease (AD). The purpose of this investigation was to determine whether phenotypic alterations in ECM production are present in non-neuronal AD cells associated with different FGF expression and response. Synthesis of glycosaminoglycans (GAG) and collagen were measured in skin fibroblasts from patients with familial, sporadic AD (FAD and SAD respectively), and from age-matched controls by radiolabeled precursors. Proteoglycans (PG), metalloprotease (MMP)-1, and FGF gene expressions were measured by reverse transcription-polymerase chain reaction. The results showed different ECM neosynthesis and mRNA levels in the two AD fibroblast populations. FAD accumulated more collagen and secreted less GAG than SAD. Biglycan PG was upregulated in FAD while betaglycan, syndecan, and decorin were markedly downregulated in SAD fibroblasts. We found a significant decrease of MMP1, more marked in FAD than in SAD fibroblasts. Constitutive FGF expression was greatly reduced in both pathological conditions (SAD>FAD). Moreover, an inverse high affinity/low affinity FGF receptor ratio between SAD and FAD fibroblasts was observed. FGF treatment differently modulated ECM molecule production and gene expression in the two cell populations. These observations in association with the changes in FGF gene expression and in the FGF receptor number, suggest that cellular mechanisms downstream from FGF receptor binding are involved in the two different forms of AD.

Effect of fibroblast growth factor-2 on equine mesenchymal stem cell monolayer expansion and chondrogenesis

OBJECTIVE

To determine whether fibroblast growth factor-2 (FGF-2) treatment of equine mesenchymal stem cells (MSCs) during monolayer expansion enhances subsequent chondrogenesis in a 3-dimensional culture system.

ANIMALS

6 healthy horses, 6 months to 5 years of age.

PROCEDURES

Bone marrow-derived MSCs were obtained from 6 horses. First-passage MSCs were seeded as monolayers at 10,000 cells/cm(2) and in medium containing 0, 1, 10, or 100 ng of FGF-2/mL. After 6 days, MSCs were transferred to pellet cultures (200,000 cells/pellet) and maintained in chondrogenic medium. Pellets were collected after 15 days. Pellets were analyzed for collagen type II content by use of an ELISA, total glycosaminoglycan content by use of the dimethylmethylene blue dye-binding assay, and DNA content by use of fluorometric quantification. Semiquantitative PCR assay was performed to assess relative concentrations of collagen type II and aggrecan mRNAs.

RESULTS

Use of 100 ng of FGF-2/mL significantly increased pellet DNA and glycosaminoglycan content. Collagen type II content of the pellet was also increased by use of 10 and 100 ng of FGF-2/mL. Collagen type II and aggrecan mRNA transcripts were increased by treatment with FGF-2. Some control samples had minimal evidence of collagen type II and aggrecan transcripts after 35 cycles of amplification.

CONCLUSIONS AND CLINICAL RELEVANCE

FGF-2 treatment of bone marrow-derived MSC monolayers enhanced subsequent chondrogenic differentiation in a 3-dimensional culture. This result is important for tissue engineering strategies dependent on MSC expansion for cartilage repair.

Protein tyrosine kinase and estrogen receptor-dependent pathways regulate the synthesis and distribution of glycosaminoglycans/proteoglycans produced by two human colon cancer cell lines

The soy isoflavone genistein can affect cell metabolism by specifically inhibiting protein tyrosine kinase (PTK) and/or interacting with the estrogen receptors (ERs). Glycosaminoglycans (GAG)/proteoglycans (PG) may participate in tumor development and progression. The synthesis of GAG by two human colon cancer cell lines, HT-29 and SW-1116, and the effects of genistein on their production and distribution between culture medium and cell membrane were studied. The mitogenic activity of genistein on both cell lines growth was also examined. Metabolic labeling, sensitive high pressure liquid chromatography (HPLC) techniques and fluorometric cell proliferation assays were utilized. The results demonstrate that both estrogen receptor beta-positive (ERbeta+) cancer cell lines produced hyaluronan (HA), both extracellular and membrane-associated galactosaminoglycans (GalAG) and heparan sulfate (HS), with the HT-29 cells producing all GAG fractions at significantly higher rates. The observed dose-dependent inhibitory effect of genistein on the synthesis of both secreted and cell-associated GAG/PG by the SW-1116 cells, as well as on their growth, was suggestive of a PTK mechanism. On the other hand, the synthesis of GAGs/PGs by HT-29 cells in the presence of genistein was dependent on their type and localization which implies the active participation of the ERs, which was further supported by the observed growth stimulation at low concentrations of genistein.

C-type natriuretic peptide regulates cellular condensation and glycosaminoglycan synthesis during chondrogenesis

C-type natriuretic peptide (CNP) has recently been identified as a key anabolic regulator of endochondral bone growth, but the cellular and molecular mechanisms involved are incompletely understood. Although CNP has been shown to stimulate proliferation and hypertrophic differentiation of growth plate chondrocytes, it is unknown whether CNP affects the earliest stages of endochondral bone development, condensation of mesenchymal precursor cells, and chondrogenesis. Here we demonstrate that CNP increases the number of chondrogenic condensations of mouse embryonic limb bud cells in micromass culture. This is accompanied by increased expression of the cell adhesion molecule N-cadherin. In addition, CNP stimulates glycosaminoglycan synthesis as indicated by increased Alcian blue staining. However, expression of the chondrogenic transcription factors Sox9, -5, and -6 or of the main extracellular matrix genes encoding collagen II and aggrecan is not affected by CNP. Instead, we show that CNP increases expression of enzymes involved in chondroitin sulfate synthesis, a required step in the production of cartilage glycosaminoglycans. In summary, we demonstrate a novel role of CNP in promoting chondrogenesis by stimulating expression of molecules involved in cell adhesion molecules and glycosaminoglycan synthesis.

Biosynthesis and structure of the basement membrane proteoglycan containing heparan sulphate side-chains

Endothelial, epithelial and muscle cells produce a similar proteoglycan for deposition in basement membrane. This proteoglycan is initially synthesized as a low buoyant density proteoglycan containing 3-5 heparan sulphate side-chains (15,000-65,000 Mr each), along one half of a 400,000 Mr core protein. A portion of the population of these macromolecules is degraded to produce small high density proteoglycans containing a variable-sized core protein less than 100,000 in Mr. This biosynthetic and degradative process probably accounts for the variety of differently sized heparan sulphate proteoglycans that have been isolated from various basement membrane sources.

Choroidal regulation of scleral glycosaminoglycan synthesis during recovery from induced myopia

PURPOSE

The present study was undertaken to examine the relationship between choroidal permeability and scleral glycosaminoglycan synthesis rates during the development of and recovery from form deprivation myopia.

METHODS

Form deprivation myopia was induced in chicks for 10 days and was followed by a period of unrestricted vision for 0 to 15 days (recovery). Choroidal permeability was quantified by measuring albumin leakage from choroidal blood vessels into suprachoroidal fluid using Evans blue. Scleral sulfated glycosaminoglycan synthesis was assessed on punches of sclera obtained immediately after extraction of suprachoroidal fluid for permeability measurements or after incubation with suprachoroidal fluid by measuring the amount of (35)SO(4) incorporated into glycosaminoglycans over a period of 4 hours at 37 degrees C. Suprachoroidal fluid was subjected to size fractionation and proteinase digestion to characterize the bioactive fractions from recovering and control chick eyes.

RESULTS

Recovery from prior form deprivation was associated with a significant increase in choroidal permeability, compared with that of myopic eyes and contralateral control eyes, and was coincident with a significant decrease in scleral sulfated glycosaminoglycan synthesis rates in treated eyes compared with contralateral control eyes. Suprachoroidal fluid isolated from recovering chick eyes significantly inhibited scleral glycosaminoglycan synthesis compared with suprachoroidal fluid from control eyes (-54%; P < 0.01; ANOVA). Preliminary characterization of suprachoroidal fluid suggested that all inhibitory activity in suprachoroidal fluid fractions specific to recovering eyes is present in molecular weight fractions of less than 10 kDa.

CONCLUSIONS

The results of this study suggest that increased choroidal permeability coincides with a decrease in the rate of scleral glycosaminoglycan synthesis during recovery from myopia. The authors speculate that increased choroidal permeability may represent a mechanism for controlling the rate of delivery of bioactive factors to the sclera to regulate the rate of glycosaminoglycan synthesis in the posterior sclera.

Improving culture conditions for temporomandibular joint disc tissue engineering

BACKGROUND

The temporomandibular joint (TMJ) is extremely important for activities like eating and talking, which can become painful and difficult for patients with TMJ dysfunction. Tissue engineering is a potential alternative to current surgical interventions through replacement of diseased or injured tissue with a functional construct. Since research with TMJ disc cells began relatively recently, optimal culturing conditions must be determined.

METHODS

Metabolic additives, L-glutamine, L-alanyl-L-glutamine, sodium pyruvate, and insulin, were examined for their effects on TMJ disc cells in monolayer. Effects of L-proline were examined in three-dimensional (3-D) culture at concentrations of 0, 25 and 100 mg/l.

RESULTS

The combination of L-glutamine, sodium pyruvate, and insulin improved cell proliferation rates without affecting collagen production or gene expression. No differences were observed in mechanical properties of the engineered constructs; however, collagen and glycosaminoglycan quantities normalized to cell number decreased at the highest concentration of L-proline.

CONCLUSION

This work identified supplements for 2-D monolayer expansion. Other supplements or culture conditions still need to be investigated for 3-D tissue production. This work improves upon porcine TMJ disc cell culturing conditions, taking us closer to being able to engineer the TMJ disc.

Enzymatic synthesis of glycosaminoglycan heparin

Heparin and its low molecular weight heparin derivatives, widely used as clinical anticoagulants, are acidic polysaccharide members of a family of biomacromolecules called glycosaminoglycans (GAGs). Heparin and the related heparan sulfate are biosynthesized in the Golgi apparatus of eukaryotic cells. Heparin is a polycomponent drug that currently is prepared for clinical use by extraction from animal tissues. A heparin pentasaccharide, fondaparinux, has also been prepared through chemical synthesis for use as a homogenous anticoagulant drug. Recent enabling technologies suggest that it may now be possible to synthesize heparin and its derivatives enzymatically. Moreover, new technologies including advances in synthetic carbohydrate synthesis, enzyme-based GAG synthesis, micro- and nano-display of GAGs, rapid on-line structural analysis, and microarray/microfluidic technologies might be applied to the enzymatic synthesis of heparins with defined structures and exhibiting selected activities. The advent of these new technologies also makes it possible to consider the construction of an artificial Golgi to increase our understanding of the cellular control of GAG biosyntheses in this organelle.

Cutaneous mucinosis associated with dermatomyositis and nephrogenic fibrosing dermopathy: fibroblast hyaluronan synthesis and the effect of patient serum

BACKGROUND

Dermal mucin is an amorphous gelatinous substance composed primarily of hyaluronan (HA) and sulphated glycosaminoglycans (GAGs). In primary cutaneous mucinosis, accumulation of mucin is a characteristic feature of lichen myxoedematosus, scleromyxoedema and reticular erythematous mucinosis. Secondary mucinoses are disorders where mucin deposition is an additional finding, and deposition is associated with lupus erythematosus, dermatomyositis, scleroderma and granuloma annulare. The underlying cause of the abnormal mucin deposition is unknown. An increasing number of cases of a fibromucinous scleromyxoedema-like disorder associated with renal dysfunction, recently termed nephrogenic fibrosing dermopathy (NFD), is being reported.

OBJECTIVES

To examine the synthesis of sulphated GAGs and HA by fibroblasts derived from uninvolved and involved skin of a patient with dermatomyositis and two patients with NFD, and the effect of patient serum.

METHODS

GAGs were quantified by a radiometric assay and HA was determined by an enzyme-linked HA-binding protein assay.

RESULTS

We found that fibroblasts derived from active lesions of NFD synthesize elevated levels of GAGs, and in particular HA, compared with normal controls, while serum from the patient with dermatomyositis and the two patients with NFD stimulates GAG synthesis, including HA synthesis, by both control and patient fibroblasts.

CONCLUSIONS

Fibroblasts from patients with active NFD are either activated to synthesize elevated levels of HA or contain another cell type, possibly derived from circulating fibrocytes. In both disorders, there is additionally a serum-derived factor that stimulates production of sulphated GAGs and HA by fibroblasts.

FGF2 and dexamethasone increase the production of hyaluronan in two-dimensional culture of elastic cartilage-derived cells: in vitro analyses and in vivo cartilage formation

Elastic cartilage-derived cells cultured two-dimensionally with FGF2 and corticosteroid produce gel-type masses that become mature cartilage when injected into a subcutaneous pocket. This unique method has previously been clinically applied for treatments of nasal augmentation. However, the components of the gel-type mass and the mechanism of its synthesis remain unknown. Here, we have investigated the components of the gel-type mass produced by elastic cartilage-derived cells, and whether this gel-type mass can be produced by using other cell sources or other media. Human elastic cartilage-derived cells from auricular cartilage, hyaline cartilage-derived cells from articular cartilage, and mesenchymal stem cells from synovium were cultured in three media: "redifferentiation medium" containing FGF2 and dexamethasone; "chondrogenic medium" containing bone morphogenetic protein-2, transforming growth factor-beta3, and dexamethasone specific for in vitro chondrogenesis of mesenchymal stem cells; control medium. The elastic cartilage-derived cells cultured in redifferentiation medium produced a gelatinous matrix positive for Alcian blue. During culture, the amount of chondroitin 4-sulfate, chondroitin 6-sulfate, and especially hyaluronan increased. However, the expression of RNAs for most chondrogenic genes did not increase. We also reproduced cartilage tissue formation by the injection of elastic cartilage-derived cells with the gelatinous mass into the subcutaneous space of the nude mouse. The synthesis of gelatinous matrix in vitro and the formation of cartilage tissue in vivo could be obtained only for the combination of elastic cartilage-derived cells with redifferentiation medium.

Molecular basis for acceptor substrate specificity of the human β1,3-glucuronosyltransferases GlcAT-I and GlcAT-P involved in glycosaminoglycan and HNK-1 carbohydrate epitope biosynthesis, respectively

The human beta1,3-glucuronosyltransferases galactose-beta1,3-glucuronosyltransferase I (GlcAT-I) and galactose-beta1,3-glucuronosyltransferase P (GlcAT-P) are key enzymes involved in proteoglycan and HNK-1 carbohydrate epitope synthesis, respectively. Analysis of their acceptor specificity revealed that GlcAT-I was selective toward Galbeta1,3Gal (referred to as Gal2-Gal1), whereas GlcAT-P presented a broader profile. To understand the molecular basis of acceptor substrate recognition, we constructed mutants and chimeric enzymes based on multiple sequence alignment and structural information. The drastic effect of mutations of Glu227, Arg247, Asp252, and Glu281 on GlcAT-I activity indicated a key role for the hydrogen bond network formed by these four conserved residues in dictating Gal2 binding. Investigation of GlcAT-I determinants governing Gal1 recognition showed that Trp243 could not be replaced by its counterpart Phe in GlcAT-P. This result combined with molecular modeling provided evidence for the importance of stacking interactions with Trp at position 243 in the selectivity of GlcAT-I toward Galbeta1,3Gal. Mutation of Gln318 predicted to be hydrogen-bonded to 6-hydroxyl of Gal1 had little effect on GlcAT-I activity, reinforcing the role of Trp243 in Gal1 binding. Substitution of Phe245 in GlcAT-P by Ala selectively abolished Galbeta1,3Gal activity, also highlighting the importance of an aromatic residue at this position in defining the specificity of GlcAT-P. Finally, substituting Phe245, Val320, or Asn321 in GlcAT-P predicted to interact with N-acetylglucosamine (GlcNAc), by their counterpart in GlcAT-I, moderately affected the activity toward the reference substrate of GlcAT-P, N-acetyllactosamine, indicating that its active site tolerates amino acid substitutions, an observation that parallels its promiscuous substrate profile. Taken together, the data clearly define key residues governing the specificity of beta1,3-glucuronosyltransferases.

Glycosaminoglycans and proteoglycans: overlooked entities?

BACKGROUND

By virtue of their high net negative charge, glycosaminoglycans and proteoglycans play pivotal roles in biologic processes such as cell-cell and cell-matrix interactions, sequestration of growth factors, activation of chemokines and cytokines, and permselectivity of basement membranes.

METHODS

The present article reviews the putative roles of glycosaminoglycans and proteoglycans in the peritoneal cavity during normal peritoneal homeostasis and chronic inflammation, the latter induced by constant exposure of the peritoneum to non-physiologic peritoneal dialysis (PD) solutions.

RESULTS

Glycosaminoglycans have been identified in the mesothelial glycocalyx, a slippery, non-adhesive layer that protects the peritoneal membrane from abrasion and infection. Dermatan sulfate proteoglycans can neutralize the activity of transforming growth factor beta1 and can thus play an essential role in modulating peritoneal fibrosis. Heparan sulfate proteoglycans play a crucial role in the sequestration of growth factors; they also modulate selective permeability of proteins across the peritoneal cavity. Reduced expression of perlecan, a heparan sulfate proteoglycan of the basement membrane, is observed in peritoneal biopsies obtained from established PD patients, consequent to prolonged exposure to the elevated glucose concentrations in conventional PD solutions. Supplementation of PD fluids with glycosaminoglycans has been shown to be beneficial to both the structural and functional integrity of the peritoneum.

CONCLUSIONS

Recent advances in the field of glycobiology have revealed a multitude of biologic processes that are controlled or influenced by glycosaminoglycans and proteoglycans. Altered synthesis of these macromolecules during PD has serious implications for the peritoneal transport of proteins, host defense, wound healing, inflammation, and fibrosis.

Polycystic disease caused by deficiency in xylosyltransferase 2, an initiating enzyme of glycosaminoglycan biosynthesis

The basic biochemical mechanisms underlying many heritable human polycystic diseases are unknown despite evidence that most cases are caused by mutations in members of several protein families, the most prominent being the polycystin gene family, whose products are found on the primary cilia, or due to mutations in posttranslational processing and transport. Inherited polycystic kidney disease, the most prevalent polycystic disease, currently affects approximately 500,000 people in the United States. Decreases in proteoglycans (PGs) have been found in tissues and cultured cells from patients who suffer from autosomal dominant polycystic kidney disease, and this PG decrease has been hypothesized to be responsible for cystogenesis. This is possible because alterations in PG concentrations would be predicted to disrupt many homeostatic mechanisms of growth, development, and metabolism. To test this hypothesis, we have generated mice lacking xylosyltransferase 2 (XylT2), an enzyme involved in PG biosynthesis. Here we show that inactivation of XylT2 results in a substantial reduction in PGs and a phenotype characteristic of many aspects of polycystic liver and kidney disease, including biliary epithelial cysts, renal tubule dilation, organ fibrosis, and basement membrane abnormalities. Our findings demonstrate that alterations in PG concentrations can occur due to loss of XylT2, and that reduced PGs can induce cyst development.

Glycosaminoglycan synthesis and structure as targets for the prevention of calcific aortic valve disease

Calcific aortic valve disease is frequently driven by ageing and the obesity-associated metabolic syndrome, and the increasing impact of these factors indicates that valve disease will become a cardiovascular disease of considerable significance. This disease is now thought to be an active cell-based disease process, which may therefore be amenable to therapeutic intervention. Some similarities are apparent with atherosclerosis. The accumulation of lipid, possibly by retention by proteoglycans and the attraction of inflammatory cells by hyaluronan, may be common to the early stages of both pathologies. The synthesis and structure of glycosaminoglycans, proteoglycans, and hyaluronan are exquisitely regulated, and the signalling pathways controlling these processes may provide tissue-specific opportunities for concomitant prevention of atherosclerosis and calcific aortic valve disease.

Composite chondroitin-6-sulfate/dermatan sulfate/chitosan scaffolds for cartilage tissue engineering

Conjugating a single glycosaminoglycan (GAG) species such as chondroitin-6-sulfate (CSC) to chitosan is beneficial to chondrocyte culture and extracellular matrix (ECM) production, but whether fabrication of 3D chitosan scaffolds with additional minor GAG species such as dermatan sulfate (DS) further improves the ECM production is unknown. In this study, Response Surface Methodology (RSM) was employed to design CSC/DS/chitosan scaffolds of various formulations for cartilage engineering and to investigate the roles of individual GAG species in cartilage formation. The CSC/DS formulation affected neither the physical properties of scaffolds nor cell adhesion, but influenced cell morphology, GAGs and collagen production and chondrocytic gene expression. The linear effects elucidated by RSM analysis suggested that within the level range higher CSC levels favored GAGs and collagen production, whereas lower DS levels were desired for these responses. Nonetheless, the quadratic effects of DS and two-way interactions between CSC and DS also contributed to the GAGs and collagen production. Accordingly, the optimal formulation, as predicted by RSM and validated by experiments, comprised 2.8 mg CSC and 0.01 mg DS per scaffold. This study confirmed the importance of DS in cartilage tissue engineering and implicated the feasibility of rational CSC/DS/chitosan scaffold design with the aid of RSM.

Agonists of peroxisome proliferators-activated receptors (PPAR) alpha, beta/delta or gamma reduce transforming growth factor (TGF)-beta-induced proteoglycans' production in chondrocytes

OBJECTIVE

To investigate the potency of selective agonists of peroxisome proliferators-activated receptors' (PPAR) isotypes (alpha, beta/delta or gamma) to modulate the stimulating effect of transforming growth factor-beta1 (TGF-beta1) on proteoglycans' (PGs) synthesis in chondrocytes.

METHOD

Rat chondrocytes embedded in alginate beads and cultured under low serum conditions were exposed to TGF-beta1 (10 ng/ml), alone or in combination with the following agonists: Wy14643 for PPARalpha, GW501516 for PPARbeta/delta, rosiglitazone (ROSI) for PPARgamma, in the presence or absence of PPAR antagonists (GW6471 for PPARalpha, GW9662 for PPARgamma). PGs' synthesis was evaluated by radiolabelled sulphate incorporation and glycosaminoglycans' (GAGs) content by Alcian blue staining of beads and colorimetric 1.9 dimethyl-methylene blue assay after beads' solubilization. Phosphorylation of Extracellular Signal-related Kinase1/2 (ERK1/2), Smad2/3 and p38-MAPK was assessed by Western Blot and production of prostaglandin E2 (PGE2) by Enzyme immuno-assay (EIA). Levels of mRNA for PPAR target genes [acyl-CoA oxidase (ACO) for PPARalpha; mitochondrial carnitin palmitoyl transferase-1 (CPT-1) for PPARbeta/delta and adiponectin for PPARgamma], aggrecan, TGF-beta1 and genes controlling GAGs' side chains' synthesis were quantified by real time polymerase chain reaction and normalized over RP29 housekeeping gene.

RESULTS

ACO was selectively up-regulated by 100 microM of Wy14643, CPT-1 by 100 nM of GW501516 and adiponectin by 10 microM of ROSI without cell toxicity. TGF-beta1 increased PGs' synthesis by four-fold, GAGs' content and deposition by 3.5-fold and six-fold, respectively, while inducing aggrecan expression around 10-fold without modifying mRNA levels of GAGs' controlling enzymes. PPAR agonists inhibited the stimulating effect of TGF-beta1 by 24-44% on PGs' synthesis and over 75% on aggrecan, GAGs' content and deposition with the following rank order of potency: ROSI>GW501516> or =Wy14643. TGF-beta1-induced phosphorylation of Smad2/3 and ERK1/2 was reduced by ROSI over GW501516 but not by Wy14643 whereas stimulated PGE2 production was inhibited by Wy14643 over GW501516 but not by ROSI. The effect of PPAR agonists on PPAR target genes and TGF-beta1-induced aggrecan expression was reversed selectively by PPAR antagonists.

CONCLUSION

In chondrocytes' beads, PPAR agonists reduced the stimulating effect of TGF-beta1 on PGs by inhibiting TGF-beta1-induced aggrecan expression in an isotype-selective manner. Thus, PPAR agonists could be deleterious in situation of cartilage repair although being protective in situation of cartilage degradation.

Injectable biodegradable hydrogel composites for rabbit marrow mesenchymal stem cell and growth factor delivery for cartilage tissue engineering

We investigated the development of an injectable, biodegradable hydrogel composite of oligo(poly(ethylene glycol) fumarate) (OPF) with encapsulated rabbit marrow mesenchymal stem cells (MSCs) and gelatin microparticles (MPs) loaded with transforming growth factor-beta1 (TGF-beta1) for cartilage tissue engineering applications. Rabbit MSCs and TGF-beta1-loaded MPs were mixed with OPF, a poly(ethylene glycol)-diacrylate crosslinker and the radical initiators ammonium persulfate and N,N,N',N'-tetramethylethylenediamine, and then crosslinked at 37 degrees C for 8 min to form hydrogel composites. Three studies were conducted over 14 days in order to examine the effects of: (1) the composite formulation, (2) the MSC seeding density, and (3) the TGF-beta1 concentration on the chondrogenic differentiation of encapsulated rabbit MSCs. Bioassay results showed no significant difference in DNA amount between groups, however, groups with MPs had a significant increase in glycosaminoglycan content per DNA starting at day 7 as compared to controls at day 0. Chondrocyte-specific gene expression of type II collagen and aggrecan were only evident in groups containing TGF-beta1-loaded MPs and varied with TGF-beta1 concentration in a dose-dependent manner. Specifically, type II collagen gene expression exhibited a 161+/-49-fold increase and aggrecan gene expression a 221+/-151-fold increase after 14 days with the highest dose of TGF-beta1 (16 ng/ml). These results indicate that encapsulated rabbit MSCs remained viable over the culture period and differentiated into chondrocyte-like cells, thus suggesting the potential of OPF composite hydrogels as part of a novel strategy for localized delivery of stem cells and bioactive molecules.

Cellular events associated with the initial phase of AA amyloidogenesis: insights from a human monocyte model

Reactive amyloidosis is a systemic protein deposition disease that develops in association with chronic inflammation. The deposits are composed of extracellular, fibrillar masses of amyloid A (AA) protein, an N-terminal fragment of the acute-phase serum protein serum amyloid A (SAA). The pathogenic conversion of SAA into amyloid has been studied in two human cell culture models, peritoneal cells and peripheral blood monocytes. Human monocyte cultures proved more robust than either mouse or human peritoneal cells at initiating amyloid formation in the absence of a preformed nidus such as amyloid-enhancing factor and particularly well suited for examination of individual cells undergoing amyloid formation. Amyloid-producing monocyte cultures were stained with Congo red and Alcian blue for detection of amyloid and glycosaminglycans, respectively; immunocytochemistry was performed to identify SAA/AA, CD68, CD14, lysosomal protein Lamp-1, and early endosomal protein EEA1. SAA interaction with monocytes was also visualized directly via fluorescence confocal microscopy. Amyloid was initially detected only in intracellular vesicles, but with time was seen extracellularly. Morphologic changes in lysosomes were noted during the early phase of amyloid formation, suggesting that exocytosis of fibrils may occur via lysosome-derived vesicles. Cultures engaged in amyloid formation remained metabolically active; no cytotoxic effects were observed. Mimicking in vivo phenomena, amyloid formation was accompanied by increased glycosaminoglycan content and C-terminal processing of SAA. The ability of human monocytes to endocytose and intracellularly transform SAA into amyloid via a mechanism that requires and maintains, rather than compromises, metabolic activity distinguishes them as a useful model for probing earliest events in the disease process.

Impairment of chondrocyte biosynthetic activity by exposure to 3-tesla high-field magnetic resonance imaging is temporary

The influence of magnetic resonance imaging (MRI) devices at high field strengths on living tissues is unknown. We investigated the effects of a 3-tesla electromagnetic field (EMF) on the biosynthetic activity of bovine articular cartilage. Bovine articular cartilage was obtained from juvenile and adult animals. Whole joints or cartilage explants were subjected to a pulsed 3-tesla EMF; controls were left unexposed. Synthesis of sulfated glycosaminoglycans (sGAGs) was measured by using [³⁵S]sulfate incorporation; mRNA encoding the cartilage markers aggrecan and type II collagen, as well as IL-1β, were analyzed by RT–PCR. Furthermore, effects of the 3-tesla EMF were determined over the course of time directly after exposure (day 0) and at days 3 and 6. In addition, the influence of a 1.5-tesla EMF on cartilage sGAG synthesis was evaluated. Chondrocyte cell death was assessed by staining with Annexin V and TdT-mediated dUTP nick end labelling (TUNEL). Exposure to the EMF resulted in a significant decrease in cartilage macromolecule synthesis. Gene expression of both aggrecan and IL-1β, but not of collagen type II, was reduced in comparison with controls. Staining with Annexin V and TUNEL revealed no evidence of cell death. Interestingly, chondrocytes regained their biosynthetic activity within 3 days after exposure, as shown by proteoglycan synthesis rate and mRNA expression levels. Cartilage samples exposed to a 1.5-tesla EMF remained unaffected. Although MRI devices with a field strength of more than 1.5 T provide a better signal-to-noise ratio and thereby higher spatial resolution, their high field strength impairs the biosynthetic activity of articular chondrocytes in vitro. Although this decrease in biosynthetic activity seems to be transient, articular cartilage exposed to high-energy EMF may become vulnerable to damage.

Exogenous sphingomyelinase increases collagen and sulphated glycosaminoglycan production by primary articular chondrocytes: an in vitro study

We previously established a role for the second messenger ceramide in protein kinase R (PKR)-mediated articular cartilage degradation. Ceramide is known to play a dual role in collagen gene regulation, with the effect of ceramide on collagen promoter activity being dependent on its concentration. Treatment of cells with low doses of sphingomyelinase produces small increases in endogenous ceramide. We investigated whether ceramide influences articular chondrocyte matrix homeostasis and, if so, the role of PKR in this process. Bovine articular chondrocytes were stimulated for 7 days with sphingomyelinase to increase endogenous levels of ceramide. To inhibit PKR, 2-aminopurine was added to duplicate cultures. De novo sulphated glycosaminoglycan and collagen synthesis were measured by adding [³⁵S]-sulphate and [³H]-proline to the media, respectively. Chondrocyte phenotype was investigated using RT-PCR and Western blot analysis. Over 7 days, sphingomyelinase increased the release of newly synthesized sulphated glycosaminoglycan and collagen into the media, whereas inhibition of PKR in sphingomyelinase-treated cells reduced the level of newly synthesized sulphated glycosaminoglycan and collagen. Sphingomyelinase treated chondrocytes expressed col2a1 mRNA, which is indicative of a normal chondrocyte phenotype; however, a significant reduction in type II collagen protein was detected. Therefore, small increments in endogenous ceramide in chondrocytes appear to push the homeostatic balance toward extracellular matrix synthesis but at the expense of the chondrocytic phenotype, which was, in part, mediated by PKR.

Changes in steroid receptors and proteoglycan expression in the guinea pig prostate stroma during puberty and hormone manipulation

BACKGROUND

Proteoglycans are structural and informational molecules important during embryogenesis and organ maturation. Maturation of the prostate is influenced by androgens and estrogens, but changes in the relative spatiotemporal expression of steroid receptors and proteoglycans during hormonal change are unexplored.

METHODS

Guinea pig prostate was used to define hormone-induced changes in the expression of androgen (AR) and estrogen (ER(alpha)) receptors, chondroitin sulfate (CS) glycosaminoglycan and core proteins of versican and syndecan-1. Tissue locations of AR, ER(alpha), CS and the proteoglycans versican and syndecan-1 were determined by immunohistochemistry. Cellular content of ER(alpha) and syndecan-1 was assessed visually. Versican, CS56 epitope, and AR were quantified by image analysis.

RESULTS

AR expression within prostate epithelial and stromal cell nuclei decreased following castration and increased following treatment of castrate animals with dihydrotestosterone (DHT). ER(alpha) expression was restricted to prostate stromal cell nuclei and decreased during puberty, and following treatment of castrate animals with DHT. Versican was present in periacinar stroma immediately peripheral to basal epithelial cells, fibromuscular stromal tissue bands surrounding acinar units, and loose fibrovascular connective tissue interspersed between individual acini. Versican and native CS expression decreased (>10-fold) in periacinar stroma during puberty and following administration of DHT to castrated animals. Expression of syndecan-1 was restricted to fibromuscular cells of prostate stroma, and remained constant during puberty and hormone manipulation.

CONCLUSIONS

ER(alpha), versican core protein and CS side chain epitopes are negatively regulated in prostate stromal tissue by DHT, whilst AR levels are positively regulated.

Glycosaminoglycan synthesis and shedding induced by growth factors are cell and compound specific

The interactions between growth factors and sulphated glycosaminoglycans (GAG) have been extensively studied. The aim of this study is to investigate if growth factors would show specificity of action on the synthesis and shedding of sulphated GAG, using two different cell lines: endothelial and smooth muscle cells. The cells were grown in the presence or absence of growth factors: EGF, FGF2, VEGF121, VEGF165. Transfection assays were also performed using recombinant pcDNA3.1, containing VEGF165 cDNA. In order to analyse the different types of GAG the cells were metabolically labelled with [(35)S]-sulphate. At low doses, VEGF121 was the only growth factor able to increase both the synthesis and secretion of heparan sulphate (HS) in endothelial cells. Over expression of VEGF165 stimulated HS synthesis in both cells. The combined results showed that growth factors affect GAG synthesis in a cell specific and dose dependent manner.

Desmoid and fibroma tumors differently respond to TGFβ1 stimulus and ECM macromolecule accumulation

Desmoid and fibroma tumours are characterized by cell proliferation, glycosaminoglycan and collagen fibre accumulation, high levels of transforming growth factor beta(1) (TGFbeta(1)) and different patterns of tissue infiltration. TGFbeta(1) is related to extracellular matrix (ECM) composition which, in turn, regulates cell functions and cell migration. In this study we report changes in cell proliferation, glycosaminoglycan (GAG) and collagen synthesis, TGFbeta(1) mRNA expression and fibronectin levels in normal, desmoid and fibroma fibroblast cultures before and after TGFbeta(1) stimulation. Our data showed cell proliferation, GAG and collagen synthesis, transforming growth factor beta(1) mRNA expression and fibronectin levels were significantly higher in desmoid than in fibroma cultures. TGFbeta(1) treatment had no effect on cell proliferation, but increased TGFbeta(1) mRNA expression, GAG, fibronectin and collagen synthesis in desmoid and fibroma fibroblasts. Its effects were more marked in desmoid cells. Fibronectin favours cell migration, while changes in GAG composition alter cell behaviour and ECM organization. In conclusion our data suggest that the different patterns of infiltration in desmoid and fibroma tumours are due to changes in ECM components and cell-ECM interactions which can be ascribed to altered TGFbeta(1) mRNA expression and TGFbeta(1) activity.

Smoking and thyroid-associated ophthalmopathy: A novel explanation of the biological link

INTRODUCTION

Cigarette smoking is the strongest modifiable risk factor for developing thyroid-associated ophthalmopathy (TAO), and the severity of TAO is related to the current number of cigarettes smoked per day. We aimed to establish the effects of cigarette smoke extract (CSE) on an in vitro model of TAO.

METHODS

Orbital tissue was taken during surgery from 10 patients with TAO and nine control subjects. Orbital fibroblasts were cultured and exposed to CSE, and intercellular adhesion molecule 1 (ICAM1) expression was measured by flow cytometry. Glycosaminoglycan production was measured by hyaluronic acid ELISA. Orbital fibroblasts were grown in adipogenic media with or without CSE and/or IL-1, and the degree of adipogenesis was quantified.

RESULTS

Fibroblasts from patients with TAO and controls showed similar responses. ICAM1 expression was not affected by CSE. Hyaluronic acid production was stimulated by CSE in a dose-dependent manner (correlation coefficient, 0.978; P = 0.022), with 5% CSE causing an increase of 44% (P = 0.001). CSE increased adipogenesis in a dose-related manner, as did IL-1. The effects of CSE and IL-1 on adipogenesis were synergistic, with the degree of adipogenesis in the well containing both 5% CSE and 0.1 ng/ml IL-1 being double the magnitude of the sum of the values obtained from either stimulus alone (P < 0.001). Addition of an anti-IL-1 antibody to the well containing both 5% CSE and 0.1 ng/ml IL-1 reduced the degree of adipogenesis by 82% (P < 0.001).

CONCLUSION

These findings may help explain how cigarette smoking has a detrimental effect in TAO and suggests that IL-1 may be an attractive therapeutic target in TAO.